Water-soluble yellow azo dyes

ABSTRACT

A dye of the formula (2) and a process for preparing the same, wherein the radicals are as defined in the specification

The present invention describes new water-soluble yellow azo dyes,processes for preparing them and their use as recording fluids,especially for the ink-jet printing process.

The ink-jet process is a contactless printing process, where generally adistinction is made between two printing techniques: drop on demand andcontinuous stream. The drop-on-demand principle is that the ink in theform of a droplet from a nozzle is placed—under electronic control—inthe right place at the right time, whereas in continuous stream printingthe ink is delivered continuously and then, likewise after electroniccharging, either impinges on the receiving medium (paper for example) oris diverted into a collecting vessel. To obtain prints of highdefinition and resolution the recording fluids and the dyes present inthem have to meet corresponding requirements, particularly with regardto lightfastness and waterfastness. High lightfastness is of greatimportance in particular for exterior ink-jet applications and in theproduction of ink-jet prints of photographic quality.

The most important part in all this is played by the dyes used in theinks. Despite the development of a large number of dyes there are only afew which meet the requirements imposed on them in a modern-day printingoperation.

Initially water-soluble reactive dyes based on the 1,3,5-triazinestructural unit, which are used for dyeing or printing cotton fibers(textile printing), were employed. Their usefulness for producingink-jet inks for ink-jet printing, however, is only limited, since thestorage stability of the resultant inks is low and the lightfastnessesof the prints obtained are poor. If the possibility is exploited ofallowing targeted reaction of the reactive anchor of such dyes withnucleophiles, the result, for example, is yellow compounds of theformula (1) in accordance with EP-A-0 755 984:

These dyes are distinguished by high lightfastness; a drawback found,however, has been the sensitivity to hydrolysis and, consequently, a lowstability on storage.

There is therefore a need for improved colorants which are superior tothe existing yellow dyes, in particular in storage stability, and at thesame time have the other properties required for the ink-jet sector.

It has been found that the azo compounds of the formula (2) and theirtautomeric forms possess a high storage stability in conjunction withexcellent waterfastness and good lightfastness.

The present invention accordingly provides dyes of the formula (2)

in which

-   A and B are identical or different and are a C₆-C₁₀-aryl radical    which is unsubstituted or substituted by 1, 2, 3 or 4 substituents    from the group consisting of C₁-C₆-alkyl, hydroxyl, C₁-C₆-alkoxy,    carboxyl, sulfo, sulfonamide, amino and C₁-C₆-alkylamino; or are a    5- to 7-membered aromatic heterocycle which may be benzo-fused and    may carry 1, 2, 3 or 4 of the aforementioned substituents, or-   in which A is a radical of an azo dye of the formula (2a)    D¹-N═N-D²-  (2a)-    in which D¹ and D² are identical or different and are a C₆-C₁₀-aryl    radical which is unsubstituted or substituted by 1, 2, 3 or 4    substituents from the group consisting of C₁-C₆-alkyl, hydroxyl,    C₁-C₆-alkoxy, carboxyl, sulfo, sulfonamide, amino and    C₁-C₆-alkylamino;-   Y is a group which contains oxygen and/or nitrogen and which if    desired via X of the enolate function forms a 9- or 10-membered    ring;-   X is hydrogen, a monovalent metal cation, one equivalent of a    polyvalent metal cation or a C₁-C₄-alkyl-, phenyl- or    (C₁-C₄)-alkoxy-(C₁-C₄)-alkyl-substituted ammonium ion.

Preferred azo dyes of the formula (2) are those in which

-   A and B are phenyl, naphthyl, pyridyl or pyrazolyl which may be    substituted by 1 or 2 substituents from the group consisting of    methyl, ethyl, propyl, hydroxyl, methoxy, ethoxy, propoxy, carboxyl,    sulfo, sulfonamido, amino and methylamino.

Preferred azo dyes of the formula (2) are additionally those in which Ais a radical of the formula (2a) in which D¹ and D² are phenyl ornaphthyl which may be substituted by 1 or 2 substituents from the groupconsisting of methyl, ethyl, propyl, hydroxyl, methoxy, ethoxy, propoxy,carboxyl, sulfo, sulfonamido, amino and methylamino.

Preferred azo dyes of the formula (2) are additionally those in which

-   Y is hydroxyl, methoxy, carboxyl or amino.

Preferred azo dyes of the formula (2) are additionally those in which

-   X is hydrogen, Na, K or a transition metal cation.

Particularly preferred azo dyes of the formula (2) are additionallythose in which A and B are each a phenyl or naphthyl radical substitutedby 1 or 2 sulfo and/or carboxyl groups.

Particularly preferred azo dyes of the formula (2) are additionallythose in which A is a radical of the formula (2a) in which D¹ is aphenyl or naphthyl radical substituted by 1 or 2 sulfo groups and D² isa phenyl radical substituted by sulfo, hydroxyl or methoxy.

Particularly preferred azo dyes of the formula (2) are additionallythose in which X is Cu, Co, Ni, Fe or Cr which together with Y forms a9- or 10-membered ring. In particular X is Cu.

The present invention also provides a process for preparing the dyes ofthe formula (2) which comprises reacting the amine of the formula (3)A-NH₂  (3)with diketene (4)

and coupling the resulting compound of the formula (5) and/or itstautomer

with the diazonium salt of the formula (6),Y—B—N₂ ⁺Z⁻  (6)and, if desired, further reacting the coupling product with a metal saltsolution or ammonium salt solution.

The reaction of (3) with (4) takes place preferably at from 0 to 40° C.and at a pH of from 4 to 9.

The diazotization and coupling steps can be carried out in accordancewith conventional methods.

The diazotization is preferably conducted in aqueous solution orsuspension with sodium nitride at temperatures from 0 to 10° C. and at apH of between 1 and 3. The azo coupling is preferably conducted inaqueous solution or suspension at temperatures from 0 to 20° C. and at apH of between 3 and 9.

The molar ratios between the respective diazonium salt and therespective coupling component are preferably 1: (0.8 to 2).

Complexing with a metal takes place advantageously by adding an aqueousmetal salt solution, e.g. a metal sulfate, chloride, bromide, hydrogensulfate, bicarbonate or carbonate. Depending on the particular dye thecomplexing may be conducted in the acidic range and in the basic range.The temperature ought to be between 60 and 130° C.; if desired, heatingis carried out under superatmospheric pressure.

The dyes of the invention can be isolated from the as-obtained,preferably aqueous reaction mixtures by salting out, filtration or spraydrying, with or without partial or complete prior desalting by means ofmembrane filtration. However, an isolation step may also be omitted andthe reaction mixtures comprising the dyes of the invention may beconverted directly into concentrated dye solutions by adding organicand/or inorganic bases and/or humectants and, if desired, after partialor complete desalting by means of membrane filtration. Alternatively thecomplex dyes may also be used as presscakes (in flushing processes aswell, if appropriate) or as powders. For further purification, the dyesin the form of their aqueous solutions can be passed over an ionexchange resin.

The dyes of the invention may further comprise a shading colorant,preferably from the group of the colorants listed in the Colour Index,such as C.I. Acid Yellow 17 and 23, C.I. Direct Yellow 86, 98 and 132,C.I. Reactive Yellow 37, C.I. Pigment Yellow 17, 74, 83, 97,120, 139,151, 155 and 180; C.I. Direct Red 1, 11, 37, 62, 75, 81, 87, 89, 95,227; C.I. Acid Red 1, 8, 80, 81, 82, 87, 94, 115, 131, 144, 152, 154,186, 245, 249 and 289; C.I. Reactive Red 21, 22, 23, 35, 63, 106, 107,112, 113, 114, 126, 127, 128, 129, 130, 131, 137, 160, 161, 174, 180;C.I. Pigment Red 122, 176, 184, 185 and 269; C.I. Direct Blue 199, C.I.Acid Blue 9, C.I. Pigment Blue 15:1-15:4. The shading colorant ispreferably present in an amount of from 0.001 to 5% by weight, inparticular from 0.01 to 1% by weight, based on the dry weight of the dyeof the invention.

The dyes of the invention can be mixed with the shading colorant bymixing the dyes of the formula (2) and the shading colorant with oneanother in the proportions indicated in the form of dry powders,solutions thereof, water- or solvent-moist presscakes and/ormasterbatches, or inks produced from the dyes can be shaded.

The present invention further provides for the use of the (shaded orunshaded) dyes of the formula (2) for dyeing and printing natural andsynthetic fiber materials, such as polyester, silk, wool or blendfabrics, for example, particularly for the recording of text and imageson various recording media, and also for pulp coloring paper orcelluloses.

For use in recording fluids the dyes described are prepared inaccordance with the stated requirements. The dyes can be isolated fromthe as-obtained, preferably aqueous reaction mixtures by salting out andfiltration or by spray drying, if desired after partial or completedesalting by means of membrane filtration and/or ion exchange. Analternative is to dispense with isolation and to convert thedye-containing reaction mixtures directly into concentrated dyesolutions by adding organic and/or inorganic bases, possibly humectants,preservatives and, if desired, after partial or complete desalting bymeans of membrane filtration. Alternatively the dyes may also be used aspresscakes (in flushing processes as well, if appropriate) or aspowders. Advantageously the dyes of the invention are used as far aspossible in pure and salt-free form, i.e., free from NaCl or othercustomary inorganic salts formed during the synthesis of the dyes.

Examples of inorganic bases suitable for concentrated dye solutionsinclude lithium hydroxide, lithium carbonate, sodium hydroxide, sodiumhydrogencarbonate, sodium carbonate, potassium hydroxide, potassiumcarbonate and ammonia. Examples of suitable organic bases includemonoethanolamine, diethanolamine, triethanolamine, 2-aminopropanol,3-aminopropanol, dipropanolamine, tripropanolamine,N-methylaminoethanol, N,N-dimethylaminoethanol, N-phenylaminopropanol,ethylenediamine, tetramethylethylenediamine,tetramethylpropylenediamine, tetramethylhexylenediamine,diethylenetriamine, triethylenetetramine, triethylamine,diisopropylethylamine and polyethyleneimine.

Examples of humectants suitable for concentrated dye solutions includeformamide, urea, tetramethylurea, ε-caprolactam, ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycol, butylglycol, methyl Cellosolve, glycerol, N-methylpyrrolidone,1,3-diethyl-2-imidazolidinone, sodium xylenesulfonate, sodiumcumenesulfonate and sodium butyl monoglycol sulfate.

The dyes of the invention are particularly suitable for producingrecording fluids, especially inks on an aqueous and non-aqueous basisfor the ink-jet printing process, and also for those inks which operatein accordance with the hot-melt process or are based on microemulsions,but also for other printing, reproduction, marking, writing, drawing,stamping or registration processes.

The present invention additionally provides recording fluids whichcomprise a dye of the invention and, if desired, other colorants forshading, as described above. Shading colorants of this kind areadvantageously present in an amount of from 0 to 20% by weight,preferably from 0.01 to 10% by weight, in particular from 0.1 to 5% byweight, based on the total weight of the recording fluid.

The composition of the recording fluid must be adapted to the particularend use.

Recording fluids of the invention generally contain in total from 0.1 to50% by weight of the dye of the formula (2) and, if desired, the shadingcolorant, calculated as dry weight, from 0 to 99% by weight of water andfrom 0.5 to 99.5% by weight of organic solvent and/or humectant. In onepreferred embodiment the recording fluids contain from 0.5 to 15% byweight of said dye, calculated as dry weight, from 35 to 75% by weightof water and from 10 to 50% by weight of organic solvent and/orhumectant; in another preferred embodiment from 0.5 to 15% by weight ofsaid dye, calculated as dry weight, from 0 to 20% by weight of water andfrom 70 to 99.5% by weight of organic solvent and/or humectant.

The dyes (2) and recording fluids comprising them are prepared usingwater preferably in the form of distilled or demineralized water.

The solvents and/or humectants present in the recording fluids maycomprise an organic solvent or a mixture of such solvents, preferencebeing given to water-miscible solvents. Suitable solvents are, forexample, monohydric or polyhydric alcohols, their ethers and esters,e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol;dihydric or trihydric alcohols, in particular with 2 to 6 carbon atoms,e.g., ethylene glycol, propylene glycol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol,glycerol, diethylene glycol, dipropylene glycol, triethylene glycol,polyethylene glycol, tripropylene glycol, polypropylene glycol; loweralkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl,monoethyl or monobutyl ether, triethylene glycol monomethyl or monoethylether, for example; ketones and ketone alcohols such as acetone, methylethyl ketone, diethyl ketone, methyl isobutyl ketone, methyl pentylketone, cyclopentanone, cyclohexanone and diacetone alcohol, forexample; amides, such as dimethylformamide, dimethylacetamide andN-methylpyrrolidone, for example; and also urea, tetramethylurea,thiodiglycol and ε-caprolactam.

The recording fluids of the invention may further comprise customaryadditives, examples being preservatives, cationic, anionic or nonionicsurface-active substances (surfactants and wetting agents), and agentsfor regulating the viscosity, e.g., polyvinyl alcohol, cellulosederivatives, or water-soluble natural or synthetic resins as filmformers and/or binders for increasing the adhesion and abrasionresistance. Additionally it is possible for light stabilizers, opticalbrighteners, oxidizing agents, reducing agents and free-radicalscavengers to be present.

It is additionally possible for amines to be present, such asethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine,diisopropylamine or N-ethyldiisopropylamine, for example, in order toincrease the pH of the recording fluid, normally at from 0 to 10% byweight, preferably from 0.5 to 5% by weight, based on the total weightof the recording fluid.

Depending on the embodiment of this ink-jet printing process, as forexample a continuous jet, intermittent jet, impulse jet or compound jetprocess, the recording fluids may be admixed with further additives, forthe purpose for example of buffering the pH, adjusting the electricalconductivity, the specific heat capacity, the thermal expansioncoefficient and the conductivity.

In the storage of recording fluids of the invention there is nosedimentation of precipitates leading to poorly defined prints or nozzleclogging.

In terms of viscosity and surface tension the recording fluids of theinvention are within the ranges appropriate for ink-jet processes. Theygive prints of high optical density with excellent lightfastness andwaterfastness.

Additionally the dyes of the invention could be used as an ink set incombination with magenta, cyan and black colorants. The magenta, cyanand black shades involve not only dyes, such as the C.I. dyes ReactiveRed 23, C.I. Reactive Red 180, C.I. Acid Red 52, C.I. Acid Blue 9 andC.I. Direct Blue 199, but also pigments, such as C.I. Pigment Red 122,C.I. Pigment Red 176, C.I. Pigment Red 184, C.I. Pigment Red 185 andC.I. Pigment Red 269, C.I. Pigment Violet 19, C.I. Pigment Blue 15, C.I.Pigment Blue 15:3 and C.I. Pigment Blue 15:4. Black shades are formedfor the dyes C.I. Reactive Black 8, C.I. Reactive Black 31, C.I. DirectBlack 168, C.I. Sol. Sulfur Black 1 and 2, C.I. Acid Black 194 andcarbon black.

The dye mixtures of the invention are further suitable as colorants inelectrophotographic toners and developers, such as one-component andtwo-component powder toners, magnetic toners, liquid toners,polymerization toners and other, specialty toners, for example.

Typical toner binders are addition polymerization, polyaddition andpolycondensation resins, such as styrene, styrene-acrylate,styrene-butadiene, acrylate, polyester, phenolic-epoxy resins,polysulfones, polyurethanes, individually or in combination, and alsopolyethylene or polypropylene, which may also contain furtheringredients, such as charge control agents, waxes or flow agents, or mayhave such ingredients added subsequently.

The dye mixtures of the invention are suitable, furthermore, ascolorants in powders and powder coating materials, particularly intriboelectrically or electrostatically sprayed powder coating materials,which are employed for the surface coating of articles made for examplefrom metal, wood, plastic, glass, ceramic, concrete, textile material,paper or rubber.

Powder coating resins used are typically epoxy resins carboxyl- andhydroxyl-containing polyester resins, polyurethane and acrylic resins,together with customary curing agents. Combinations of resins are alsoused. Thus, for example, epoxy resins are frequently used in combinationwith carboxyl- and hydroxyl-containing polyester resins.

The dyes of the invention are also suitable as colorants for colorfilters, both for additive and for subtractive color generation, andalso as colorants in electronic inks for “electronic newspapers” and inthe medical sector.

In addition to these applications the azo dyes of the invention are alsosuitable as colorants in printing inks, varnishes, paints, plastics,rubber materials, office articles, wood stain and cleaning products, andartist's colors. Typical printing inks are, for example, offset printinginks, illustration gravure inks, and printing inks for aqueous andsolvent-based packaging printing and flexographic printing. Typicalcoating materials are automotive OEM and refinish materials, industrialcoating materials and architectural paints (e.g., polymer renders oremulsion paints). Examples of typical plastics coloring systems arethose in plasticized and unplasticized PVC (polyvinyl chloride),polyolefins or polystyrenes.

The dyes of the invention can be used, moreover, for coating thesurfaces of articles made for example of metal, wood, plastic, glass,ceramic, concrete, textile material, paper and rubber.

In the fields of application described above, as well, the dyes of theinvention may additionally be shaded with the pigments and/or dyeslisted above.

In the examples below relating to the preparation of the dyes of theinvention and of recording fluids, the lightfastness is determined inaccordance with DIN 54003 (blue wool scale).

EXAMPLE 1

Stage A: 0.06 mol of orthanilic acid are suspended in 200 ml of waterand adjusted to a pH of 6 with 10 N sodium hydroxide solution. After 5minutes of stirring at room temperature the orthanilic acid has formed aclear solution. Subsequently 0.18 mol of diketene is added dropwise overthe course of 10 minutes and the pH is maintained at from 5.5 to 6.0.The reaction is over after about 1 h.

Stage B: 0.06 mol of 3-amino4-methoxybenzenesulfonic acid are stirredinto 150 ml of water in a separate vessel and the pH is adjusted toabout 0.5 with 15 ml of 10 N hydrochloric acid. After the solution hasbeen stirred at 0 to 5° C. for 30 minutes, 0.066 mol of sodium nitriteis added and the mixture is stirred for 1 h. The nitrite excess is thenremoved with 0.75 g of amidosulfonic acid.

Stage C: For the coupling, the intermediate obtained in stage A iscooled to 10° C. and the pH is adjusted to 6. The diazonium saltsolution prepared in stage B is added thereto over the course of 30minutes and the pH is maintained at 4.0-5.0 with 20 g of sodium acetate.Reaction is complete after 1 h to give the dye (7).

Alternatively the coupler solution (stage A) can be added to the diazosolution (stage B).

The dye (7) can be added directly to an ink formulation or as describedin stage D can be reacted with a copper salt in order to increase thelightfastness further.

Stage D: The dye solution obtained from stage C is heated to 60° C., asolution consisting of 0.066 mol of copper sulfate, ammonia anddiethanolamine is added and the combined solutions are heated at about90° C. for about 1 to 2 h. This gives the dye (8) in the form of anaqueous solution. Lightfastness: 5

EXAMPLE 2

In the same way as described in example 1 (stages A-C), the amine unitused is now 2-naphthylamine-6,8-disulfonic acid and the diazo unit usedis anthranilic acid. This gives the dye (9). Lightfastness: 4

EXAMPLE 3

In the same way as described in example 1, the amine unit used is now2-[(4-amino-3-methoxyphenyl)azo]naphthalene-6,8-disulfonic acid and2-hydroxy-4-sulfoaniline as diazo unit. After the metallation step thedye (10) is obtained, which has a lightfastness of 5.

The dye solutions obtained from the examples are cooled and thensubjected to ultrafine filtration through a depth filter (0.1-0.3 μm),passed over a cation exchanger, desalted via a membrane desalting unitand then adjusted for color strength. Preservation is then achieved witha biocide (e.g., ®Proxel GXL).

EXAMPLE 4 Preparation of a Recording Fluid

2.5 g of pure dye from example 1 are introduced with stirring at 25° C.into a mixture of 20.0 g of diethylene glycol, 2.5 g ofN-methylpyrrolidone, 1.0 g of triethanolamine and 76.5 g ofdemineralized water and dissolved.

EXAMPLE 5 Preparation of a Recording Fluid

2.5 g of pure dye from example 2 are introduced with stirring at 25° C.into a mixture of 20.0 g of diethylene glycol, 2.5 g ofN-methylpyrrolidone, 1.0 g of triethanolamine, 1.0 g of urea and 75.5 gof demineralized water and dissolved.

EXAMPLE 6 Preparation of a Recording Fluid

2.5 g of pure dye from example 3 are introduced with stirring at 25° C.into a mixture of 20.0 g of diethylene glycol, 1.0 g of triethanolamine,1.0 g of urea and 78.0 g of demineralized water and dissolved.

The inks prepared in this way give yellow prints with very goodlightfastness and storage stability.

To investigate the storage stability the recording fluids prepared arestored at 60° C. for 4 weeks. After this time there are no instances ofprecipitation observed and the recording fluids can be subjected toultrafine filtration without residue.

Colorimetric investigations show no changes in relation to theevaluations made prior to the storage stability tests.

1. A recording fluid for recording text and images on recording mediacomprising at least one dye of the formula (2)

wherein A and B are identical or different and are a C₆-C₁₀-aryl radicalunsubstituted or substituted by 1, 2, 3 or 4 substituents selected fromthe group consisting of C₁-C₆-alkyl, hydroxyl, C₁-C₆-alkoxy, carboxyl,sulfo, sulfonamide, amino and C₁-C₆-alkylamino; or are a 5- to7-membered aromatic heterocycle which, optionally, is benzo-fused andoptionally carries 1, 2, 3 or 4 of the aforementioned substituentsselected from the group consisting of C₁-C₆-alkyl, hydroxyl,C₁-C₆-alkoxy, carboxyl, sulfo, sulfonamide, amino and C₁-C₆-alkylamino;Y is a group which contains oxygen and/or nitrogen and, optionally, viaX of the enolate function forms a 9- or 10-membered ring; X is hydrogen,a monovalent metal cation, one equivalent of a polyvalent metal cationor a C₁-C₄-alkyl-, phenyl- or (C₁-C₄)-alkoxy-(C₁-C₄)-alkyl-substitutedammonium ion.
 2. The recording fluid of claim 1, wherein A and B arephenyl, naphthyl, pyridyl or pyrazolyl.
 3. The recording fluid of claim1, wherein Y is hydroxyl, methoxy, carboxyl or amino.
 4. The recordingfluid of claim 1, wherein X is hydrogen, Na, K or a transition metalcation.
 5. The recording fluid of claim 1, wherein A and B are each aphenyl or naphthyl radical substituted by 1 or 2 sulfo and/or carboxylgroups.
 6. The recording fluid of claim 2, wherein A and B aresubstituted by 1or 2 substituents selected from the group consisting ofmethyl, ethyl, propyl, hydroxyl, methoxy, ethoxy, propoxy, carboxyl,sulfo, sulfonamido, amino and methylamino.
 7. An ink set comprising atleast one magenta-colored recording fluid, at least one black recordingfluid, at least one cyan-colored recording fluid and at least onerecording fluid as claimed in claim 1.